I had some in the Dam, and they were the consistency of macadamia nuts with a slight nutty taste as well. I have Mexicana A. and Tampanensis going ATM, and plan on harvesting @ 6 months (April 10th 2012
) AFAIK, the slower, lower temp grown sclerotia are better than the quick grown incubated ones, but I have no personal comparison on that.
They're not really the mind blowing experience like eating 5 grams of cubes, but they are a bit more of a sociable trip, meaning you can keep it together around others that aren't tripping.
Things are painted in broader strokes IMO. Instead of the kaleidascope type color patterns on cubes, it's more waves of soft color, and very much a more thought provoking trip.
That being said, if things aren't settled in your life, this can be a bad thing causing you to dwell on the bad rather than enjoying a nice ride, so as always, just make sure you're in good spirits before you dose.
Also, once sclerotia are harvested, the colonised grain can then be cased and you will get actual mushrooms off of them, but it's a bit trickier than growing cubes, so most people just stop at the sclerotia.
Hope it helps!